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Strong-field ionization in the tunneling regime has been extensively studied in the gas phase, including in increasingly large molecular systems. Tunnel ionization in liquids offers a way to study electron tunneling dynamics in a non-periodic medium of higher electron delocalization. Here we present results from a strong-field transient absorption experiment in liquid water. Following excitation by sub-10 fs intense near-IR pulses, we spectrally probe the valence electronic states that are accessible, focusing on dynamics within the first 100 fs. With these results, we seek to understand the importance of intermolecular electron delocalization in tunnel ionization. 

Semiheavy water (HOD) is one of the simplest molecules in which the bonds are labeled by isotope. We demonstrate that a pair of intense few-femtosecond infrared laser pulses can be used to selectively tunnel ionize along one of the two bonds. The first pulse doubly ionizes HOD, inducing rapid bond stretching and unbending. Femtoseconds later, the second pulse arrives and further ionization is selectively enhanced along the OH bond. These conclusions arise from 3D time-resolved measurements of ${\mathrm{H}}^{+}, {\mathrm{D}}^{+}$ , and ${\mathrm{O}}^{+}$ momenta following triple ionization. Published by the American Physical Society2025 

Abstract Mitochondrial genomes are known for their compact size and conserved gene order, however, recent studies employing long-read sequencing technologies have revealed the presence of atypical mitogenomes in some species. In this study, we assembled and annotated the mitogenomes of five Antarctic notothenioids, including four icefishes (Champsocephalus gunnari,C. esox,Chaenocephalus aceratus, andPseudochaenichthys georgianus) and the cold-specializedTrematomus borchgrevinki. Antarctic notothenioids are known to harbor some rearrangements in their mt genomes, however the extensive duplications in icefishes observed in our study have never been reported before. In the icefishes, we observed duplications of the protein coding geneND6, two transfer RNAs,and the control region with different copy number variants present within the same individuals and with someND6duplications appearing to follow the canonical Duplication-Degeneration-Complementation (DDC) model inC. esoxandC. gunnari. In addition, using long-read sequencing and k-mer analysis, we were able to detect extensive heteroplasmy inC. aceratusandC. esox. We also observed a large inversion in the mitogenome ofT. borchgrevinki, along with the presence of tandem repeats in its control region. This study is the first in using long-read sequencing to assemble and identify structural variants and heteroplasmy in notothenioid mitogenomes and signifies the importance of long-reads in resolving complex mitochondrial architectures. Identification of such wide-ranging structural variants in the mitogenomes of these fishes could provide insight into the genetic basis of the atypical icefish mitochondrial physiology and more generally may provide insights about their potential role in cold adaptation.